<body>  <table>    <tr><th>姓名</th><th>语文</th><th>数学</th></tr>    <tr><td>Tom</td><td>76</td><td>89</td></tr>     <tr><td>Lucy</td><td>98</td><td>90</td></tr>    <tr><td>Jimmy</td><td>100</td><td>99</td></tr>    <tr><td>John</td><td>45</td><td>12</td></tr>  </table>  <script src="jquery-1.12.4.min.js"></script>  <script>    console.log($('tr:first'));    console.log($('tr:odd'));    console.log($('tr:not(tr:first)'));  </script></body>